Swainsona formosa is the top choice for potted plants: a detailed guide to cultivation and management

Cultivation and management of Swainsona formosa, the top choice for potted plants

Cultivation and management of Swainsona formosa

①Seeds (May 8)

②Seedlings (May 12)

③Young plants (August 1)

④Mature plants (September 14)

Swainsona formosa, also known as glory pea and desert pea, is a perennial herbaceous plant of the genus Swainsona in the family Fabaceae, named by the British botanist Isaac Swainson. It is native to the arid regions of central and northwestern Australia, with an average annual rainfall of 125-250 mm and soils that are sandy and rich in calcium carbonate. The first specimen was collected and prepared by the famous British explorer William Dampier on August 22, 1699, in the "Dampier's Archipelago" of northwestern Australia, and the specimen is now kept at the Fielding-Druce Herbarium of the University of Oxford in the United Kingdom. On November 23, 1961, Swainsona formosa was officially designated the floral emblem of South Australia (related flower stamps were issued in 1968, 1971 and 2005), and locally it is a popular subject in everything from art and photography to poetry, prose and legend. Australian Aboriginal peoples roasted the seeds and made them into foods such as cakes, while the flowers were used as ornaments. Although Swainsona formosa is not an endangered species, collecting it in the wild without permission is illegal.

Swainsona formosa is a summer-growing plant (evergreen year-round). Although it is a perennial in its place of origin, it is often grown as an annual in horticulture because the plants are highly susceptible to fungal infection and death during cultivation. It likes a dry, warm, sunny environment, and mature plants can tolerate short droughts, strong light, slight frost, and loose, breathable, well-drained sandy soil. The optimum growing temperature is 18-26°C, and it is suitable for cultivation in USDA zones 9-11 (areas that are wet and rainy year-round, as well as coastal areas, are not suitable for growing it).

For potting, choose a large, deep pot (the taproot makes shallow pots unsuitable). The growing medium is prepared by mixing humus (leaf mold, peat, black soil, etc.), sand and gravel (vermiculite, perlite, akadama, limestone and other neutral or alkaline materials) and base fertilizer (either plant-based or animal-based fertilizer is fine) in a ratio of 3:1:1. During the growing season, the potting soil should be kept moist but must never become waterlogged; apply a quick-acting liquid fertilizer once every 7-10 days; in summer, 50%-60% shade is needed (the rest of the year full sun is fine); and promptly pinch out the growing tips or use chemicals to control the plant shape, because excessive vigor will cause energy to be consumed too rapidly and the number of flowers will drop sharply (especially in pots, as Swainsona formosa is the kind of plant that goes overboard with just a little fertilizer).

Bottom watering is more advantageous than watering from above. At no time should water droplets remain on the leaves and flowers for long; wipe them dry promptly with a paper towel, especially in the humid summer, when plants are highly prone to fungal infection from lingering moisture, leading to leaf drop, root rot and damping-off. Maintaining a ventilated, dry, sunny environment and using protective fungicides together with curative fungicides, inside and out, can greatly reduce the infection rate.

In its place of origin, the flowering period runs from July to March of the following year. The seasons in Australia are opposite to those in China: December to February of the following year is summer, March to May is autumn, June to August is winter, and September to November is spring. The timing of the local rainy season affects the flowering period. Swainsona formosa is bird-pollinated and has poor self-pollination ability, so it requires external intervention. Creating a warm environment can prevent the predicament of the plant dying before the fruit ripens; after seeds set, put seed bags on promptly to prevent the mature seeds from bursting and scattering. After harvest, the seeds can be stored in a dry place for several years. Indoor sowing is done after the last frost (Last Frost: the last frost of late winter or early spring each year), and outdoor sowing is done after the last frost when temperatures warm up (early or mid-May in most areas). The seeds of most leguminous plants have a water-impermeable, hard seed coat and a considerable period of physical dormancy. To adapt to its harsh local environment, Swainsona formosa seeds will wait until the next year's rains, or even several years later, before germinating. There are three ways to break dormancy:

1. Use a knife to nick a small opening away from the hilum. The pointed end of the seed is where the radicle is, so the seed coat at the blunt end should be removed. Treated seeds need only half a day to swell after soaking;

2. Use sandpaper or a file to gently abrade the seed coat, then soak in water overnight; remove and abrade again any that have not swelled;

3. Simulate the extreme high temperatures of the natural environment to soften the seed coat: place the seeds in freshly boiled water for no more than 30 seconds, then soak in water overnight.

For potting, sow one seed per pot, covering with 3 cm of soil after sowing. There is no need to cover with glass or plastic film. Place the container in a warm, bright spot, and germination will occur in 3-5 days. The seedling has a very deep taproot, and the taproot cannot tolerate any disturbance; the later the transplanting, the higher the mortality rate, and even if transplanting succeeds, the recovery period is quite long. Therefore, direct sowing is far better than transplanting. For growing in the ground, choose a ventilated, sunny area with higher elevation, with 90-120 cm between plants. To extend lifespan and increase plant vigor, it can be grafted at the cotyledon stage onto Colutea arborescens or Clianthus puniceus of the same family; the grafting survival rate is extremely high, and the plant is no longer troubled by fungi, with its lifespan extended to 3 years or even longer. Cuttings are also a good option: select new shoots with more than 3 nodes, apply rooting powder to the cut end, insert them into a well-drained medium, and keep them in a warm spot with bright, indirect light.

⑤Bud formation (October 6)

⑥Early flowering (October 9)

⑦Full bloom (October 11)

⑧Peak flowering period (October 20)

◆Protective fungicides

This type of fungicide can form a dense protective film on the crop surface that is breathable, water-permeable and light-permeable. This protective film can inhibit the germination and invasion of pathogen spores, thereby achieving the effect of sterilization and disease prevention. However, spraying must be done before the crop comes into contact with the disease or before the disease occurs to be effective. Although the curative effect is poor, the sterilization spectrum is broad, it has strong simultaneous control capability, and it is not easy for pathogens to develop resistance (for example: chlorothalonil, Bordeaux mixture, metalaxyl-mancozeb, azoxystrobin, streptomycin, etc.).

◆Curative fungicides

Also called systemic fungicides, but their application history is relatively short; they are a class of agents developed in the 1960s. When applied after pathogens invade the crop or after the crop becomes diseased, this type of fungicide can penetrate into the crop or be absorbed by the crop and translocated within it, directly killing or inhibiting the pathogens. Although their specificity is strong and the curative effect is good, they easily cause pathogenic bacteria to develop resistance (such as carbendazim, thiophanate, kasugamycin, etc.).